Akaike Information Criteria (AIC) for Weibull models with explanatory variables of gender and birth cohort (1980–1984 and 1985–1994) for patients enrolled on the US Cystic Fibrosis Foundation Patient Registry surviving their first birthday
| Model | Explanatory variable(s) | Weibull model AIC |
| A | Null (no variables) | 24 302.8 |
| B | Gender | 24 232.1 |
| C | Birth cohort | 24 128.7 |
| D | Gender and birth cohort as main effects | 24 060.3 |
| E | Gender and birth cohort with interaction | 24 062.2 |
| F | Separated models for gender | 24 232.4 |
| Male | 10 828.4 | |
| Female | 13 404.0 | |
| G | Separated models for birth cohort | 24 108.3 |
| 1980–1984 | 13 000.1 | |
| 1985–1994 | 11 108.2 |